Field
The present disclosure relates to an organic light-emitting display.
Discussion of the Background
Generally, an organic light-emitting display includes an anode, a cathode, and organic layers interposed between the anode and the cathode. The organic layers include at least an emitting layer and may further include a hole injecting layer, a hole transport layer, an electron transport layer and an electron injecting layer. In the organic light-emitting display, holes and electrons generated by the anode and the cathode may combine in an organic layer, particularly, in the emitting layer to form excitons. When an energy level of the excitons changes from an excited state to a ground state, the emitting layer may emit light of a color corresponding to the changed energy level.
A light-emitting material used in the emitting layer may be a fluorescent light-emitting material or a phosphorescent light-emitting material. Fluorescent light-emitting materials of most colors have a long life and high reliability. However, since a fluorescent light-emitting material converts only singlet excitons into light, its internal quantum efficiency is limited to a maximum of 25%. On the other hand, a phosphorescent light-emitting material can convert both singlet excitons and triplet excitons into light. Thus, the internal quantum efficiency of the phosphorescent light-emitting material is expected to be close to 100%. However, while phosphorescent light-emitting materials of some colors have a long life and are highly reliable, phosphorescent light-emitting materials of other colors have a relatively short life and low reliability.
To achieve desired levels of luminous efficiency, life, and reliability, some of the emitting layers included in one organic light-emitting display should be formed of a phosphorescent light-emitting material, and the other emitting layers should be formed of a fluorescent light-emitting material.
In addition, to increase the luminous efficiency of an organic light-emitting display, a buffer layer should be interposed between the emitting layers and the cathode. The buffer layer improves electron transfer characteristics from a cathode to the emitting layers. Further, the buffer layer blocks holes arriving from an anode from escaping from the emitting layers. Since a phosphorescent light-emitting material and a fluorescent light-emitting material are based on different emission principles, different buffer layers may be applied to an emitting layer formed of the phosphorescent light-emitting material and an emitting layer formed of the fluorescent light-emitting material.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.